Re: [Xen-devel] [PATCH] Initialize ioreq_t in hvmemul_do_io()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.05.14 at 15:20, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 22 May 2014 14:14
>> To: Andrew Cooper; Paul Durrant
>> Cc: xen-devel@xxxxxxxxxxxxx; Keir (Xen.org)
>> Subject: Re: [PATCH] Initialize ioreq_t in hvmemul_do_io()
>> 
>> >>> On 22.05.14 at 14:48, <paul.durrant@xxxxxxxxxx> wrote:
>> > All relevant fields of the ioreq_t are properly initialized but coverity
>> > complains about vp_eport being uninitialized (ID 1215178) because it is
>> > the subject of a struct copy in hvm_send_assist_req().
>> >
>> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
>> > Cc: Keir Fraser <keir@xxxxxxx>
>> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
>> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> > ---
>> >  xen/arch/x86/hvm/emulate.c |    2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
>> > index 904c71a..e516194 100644
>> > --- a/xen/arch/x86/hvm/emulate.c
>> > +++ b/xen/arch/x86/hvm/emulate.c
>> > @@ -57,7 +57,7 @@ static int hvmemul_do_io(
>> >      int value_is_ptr = (p_data == NULL);
>> >      struct vcpu *curr = current;
>> >      struct hvm_vcpu_io *vio;
>> > -    ioreq_t p;
>> > +    ioreq_t p = { 0 };
>> 
>> To be honest, I dislike fixes like this to address tool shortcomings. It's
>> not like this is giaramteed to be just a single instruction that gets
>> added (maybe the compiler can figure this, but I would want to rely
>> on it.
>> 
> 
> I could always change hvm_send_assist_req() to only copy the relevant fields 
> from the proto structure, as it used to in earlier versions of my patch.

But the structure copy is certainly more efficient than the piece-wise
copying.

Jan


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